foredom

I am operating a foredom brand motor kit similar to a dentist drill. 1/6 HP, 18,000 Rpm and is operated via a foot pedal. It has a metal handpiece that takes many accessories for carving a variety of materials. It has been working well for the past two months, but now when i press the foot pedal in order to operate it i get an electric shock! I have checked the motor brushes and they are still fine. Any ideas of what is going on and how to repair would be most helpful. thanks!